In an optical recording medium, such as a magneto-optical disc, it is known to provide a spiral guide groove or concentric guide grooves in advance on a disc and to record and/or reproduce data by taking advantage of the magneto-optical effects with the use of the preformed groove or grooves or the land between the adjoining grooves as the recording track or tracks. In general, addresses and data are recorded alternately on the recording track and data supervision is performed on the basis of the address information. With the aid of the address information, data may be recorded and/or reproduced on a block-by-block or sector-by-sector basis.
There is disclosed in the Japanese Patent Kokai Publication No. 63-8768 (1988) a technique in which a wobbling track for detecting the tracking error is recorded by frequency modulation by the timing code. With this technique, a 22.05 kHz sinusoidal carrier signal is frequency modulated on the basis of a timing code signal having a frequency much lower than that of the carrier to produce a wobbling track to obtain a tracking error signal during reproduction, with the timing code being demodulated to produce the position information. However, the volume of the recordable information is small and, when the technique is used for data storage, the optical head cannot be positioned accurately.
On the other hand, there is disclosed in the specification and drawings of the Japanese Patent Application 1-41784 (1989) a technique in which, as shown in FIG. a track 75 is offset in the direction of the track width on the basis of a baseband signal of read-only information, such as the data block address, and in which, during reproduction, the address is obtained with the aid of a so-called push-pull signal from a photodetector divided into two segments along the track direction. That is, by taking advantage of the fact that reproduction of the magneto-optical data signal 77 recorded on the track per se is not affected by the signal obtained by track offsetting, and that the address or the like information is contained in the high frequency range of the push-pull signal, while the tracking error signal is contained in the low frequency range, with these signals having different band widths, the address or the like information may be reproduced and, on the basis of the reproduced information, data may be supervised on a block-by-block basis.
As a principle, the magneto-optical signal (Mo signal) 77 recorded on the track 75 per se is not affected by the signal recorded by offsetting the track 75. However, in effect, the high-frequency components, for example, tend to leak into and affect the reproduced signals (RF) 79 of the MO signal 77 due to fluctuations in detector sensitivity and to the presence of the edge 78 of changes in the width of the track 75. It has also been shown that the more acute the edge, the more difficult it becomes to cut the groove or produce the optical disc by a stamper,
The present invention has been made with the above state of the art in mind. It is an object of the present invention to provide an optical recording medium in which the effect which the signal prerecorded by offsetting the track along its width has on the main signal recorded on the track may be diminished, and an information recording apparatus for prerecording the track on the recording medium.